Human T cell rearranging gamma genes encode membrane proteins which are expressed by a minor subset of T cells. Extensive studies have shown that TcR gamma gene rearrangements result from V gamma-J gamma recombinations. Here we analyze an unusual rearrangement involving a non-translatable sequence flanked by heptamer and nonamer signals in a Ti alpha/beta-positive T cell clone (JF1). This sequence, designated here as I gamma RS, is distinct from V, D or J elements. It is located in the first intron of the first constant region (C gamma 1) and homologous sequences are conserved in C gamma 2 introns. In JF1 cells the I gamma RS is juxtaposed to the J gamma 2 segment downstream to a V gamma 10-J gamma 1 rearrangement. The use of a cryptic splicing site induced JF1 cells to produce an aberrant large-sized transcript containing the I gamma RS 3' to the first exon of C gamma 1. Such a rearrangement occurring downstream to an inframe V gamma-J gamma junction may induce premature arrest of translation and lack of the C-terminal part of C gamma involved in gamma-protein assembly.